The involvement of carbonic anhydrases (CAs) in a myriad of biological events makes the development of new inhibitors of these metalloenzymes a hot topic in current Medicinal Chemistry. In particular, CA IX and XII are membrane-bound enzymes, responsible for tumour survival and chemoresistance. Herein, a bicyclic carbohydrate-based hydrophilic tail (imidazolidine-2-thione) has been appended to a CA-targeting pharmacophore (arylsulfonamide, coumarin) with the aim of studying the influence of the conformational restriction of the tail on the CA inhibition. For this purpose, the coupling of sulfonamido- or coumarin-based isothiocyanates with reducing 2-aminosugars, followed by the sequential acid-promoted intramolecular cyclization of the corresponding thiourea and dehydration reactions, afforded the corresponding bicyclic imidazoline-2-thiones in good overall yield. The effects of the carbohydrate configuration, the position of the sulfonamido motif on the aryl fragment, and the tether length and substitution pattern on the coumarin were analysed in the in vitro inhibition of human CAs. Regarding sulfonamido-based inhibitors, the best template turned out to be a d-galacto-configured carbohydrate residue, meta-substitution on the aryl moiety (9b), with K_i against CA XII within the low nM range (5.1 nM), and remarkable selectivity indexes (1531 for CA I and 181.9 for CA II); this provided an enhanced profile in terms of potency and selectivity compared to more flexible linear thioureas 1–4 and the drug acetazolamide (AAZ), used herein as a reference compound. For coumarins, the strongest activities were found for substituents devoid of steric hindrance (Me, Cl), and short linkages; derivatives 24h and 24a were found to be the most potent inhibitors against CA IX and XII, respectively (K_i = 6.8, 10.1 nM), and also endowed with outstanding selectivity (K_i > 100 µM against CA I, II, as off-target enzymes). Docking simulations were conducted on 9b and 24h to gain more insight into the key inhibitor–enzyme interactions.

The selective inhibition of key enzymes, such as carbonic anhydrases (CAs IX and XII), which are overexpressed in cancer tissues, has emerged as a promising strategy in cancer research. However, a multitarget approach is often preferred to achieve enhanced therapeutic outcomes. In this study, aryl sulfonamides were conjugated with a thiosemicarbazone moiety to enable dual functionality: the inhibition of CAs and the chelation of metal cations. Several structural factors were systematically modified, including the position of the sulfonamido group, the length of the linker, the nature of the aromatic residue, and the type of substituents. Tumor-associated CAs IX and XII inhibition was evaluated using the stopped-flow CO₂ hydrase assay, and the inhibition constants (K_i) were determined. The most promising compounds were further analyzed through molecular docking simulations. Metal chelation capabilities were evaluated using UV–Vis spectroscopy, while antiproliferative activities were measured using the sulforhodamine B (SBR) assay. Additionally, holotomographic 3D microscopy was employed to investigate the mechanisms of cell death. Sulfonamido-derived Schiff bases were synthesized through a three-step procedure that did not require column chromatography purification: (1) isothiocyanation of amino-sulfonamides, (2) nucleophilic addition of hydrazine, and (3) acid-promoted condensation with different aldehydes (benzaldehydes or pyridine-2-carboxaldehyde). The synthesized compounds exhibited inhibition of CAs in the low nanomolar to submicromolar range, with selectivity largely influenced by structural features. Notably, the m-sulfonamide derivative 5b, bearing a pyridin-2-yl residue, demonstrated potent and selective inhibition of CA IX (K_i = 4.9 nM) and XII (K_i = 5.6 nM). Additionally, it efficiently chelated Fe²⁺, Fe³⁺, and Cu²⁺ and showed promising antiproliferative activity (GI₅₀ 4.5–10 µM). Mechanistic studies revealed that apoptosis was involved in its mode of action. Therefore, the synergistic integration of sulfonamides and thiosemicarbazones represents an effective strategy for the development of multimodal anticancer agents.

A total of 24 novel steroidal derivatives were synthesized, including 1,3,4-thia(selena)diazolines and structurally unique spirothiadiazolines, obtained through intramolecular cyclization under standard acetylation conditions. This strategy was further extended to the construction of a novel dimeric compound bearing a thiadiazoline linker. Seleno- and thiosemicarbazone precursors were derived from various functionalized steroidal monomers and dimers via straightforward synthetic protocols. Key intermediates included aldehyde 7 and ketones 16, 19, and 24. Rotameric equilibria were observed in certain thiosemicarbazones, attributed to partial double-bond character in the N–CS bond. Cyclization yielded heterocyclic systems as epimeric mixtures, and in some cases, inseparable mixtures of isomers were obtained due to low diastereoselectivity. Full structural elucidation of epimeric pairs was achieved using 2D NMR and IR spectroscopy, with compounds 2, 3, 5, 11, 17, 27, 28a, and 28b further confirmed by single-crystal X-ray diffraction. Preliminary antiproliferative assays against human cancer cell lines revealed GI₅₀ values below 10 µM for compounds 21, 22, and 27.